Third man: Lord Mandelson said he felt a sense of 'personal loyalty' to Gordon Brown

Lord Mandelson said Gordon Brown "went to a dark place" after Tony Blair was elected leader of the Labour party.

The former business secretary claimed Mr Brown was left scarred by the festering leadership feud that followed the death of John Smith in 1994 and became an "unhappy and an aggressive man".

In an interview with The Guardian after the publication of his controversial memoirs yesterday, Lord Mandelson also hit back at former Labour leader Lord Kinnock's accusation that he had become a "caricature" of himself.

Lord Kinnock was critical of his book The Third Man, questioning whether his former protege was more interested in creating a sensation than adding to the historical record.

But Lord Mandelson told the newspaper: "Neil's comment is based on never having opened the book. It only became available (yesterday). I think people should read the book, rather than have views and words put into their mouths."

Asked why, if he believed Labour was unelectable under Mr Brown, he did not join attempts to oust him, Lord Mandelson said: "I felt a sense of personal loyalty. I felt a real bond between us and I was not going to be shaken on that.

"But it was also my guess that if Gordon stepped down and people got behind David Miliband, Ed Balls would have entered the contest, and before you knew where you were there would have been an ugly fight, not just between two people perceived to represent new and old Labour, which was the last thing we want."

Lord Mandelson said he wished he could have done more to help Mr Brown overcome his bitterness after Mr Blair's successful leadership bid.

He said: "In the aftermath of John Smith's death and Tony becoming leader, Gordon went to a dark place that was defensive, did not make friends easily, saw people repeatedly out to do him when no such threat existed...

"...therefore the Gordon I saw during the period of the Labour government was more often than not an unhappy and an aggressive man, rather than the alliance builder and team player that I had worked with previously."

He added: "I think this left a scar ... that I hoped I could remedy, and help him operate in a different way. I did so only at the margin, but I wish I could have done much more for him."

Lord Mandelson earlier denied reports that Mr Blair was "livid" about the book, saying he had been in touch with the former prime minister by text message since extracts began appearing in The Times.

The book quotes Mr Blair as describing his eventual successor as "mad, bad, dangerous and beyond redemption" and says he reneged on a promise to step down in Mr Brown's favour ahead of the 2005 general election.

Yesterday, Lord Mandelson insisted the book painted a flattering picture of the two men who led the New Labour government.

And during an appearance on ITV1's This Morning, he copied out a message he received from Mr Blair on his BlackBerry, which was later read out on air by presenter Phillip Schofield.

It read: "I have specifically said to all who have asked that I am NOT angry!"

Mr Blair is due to publish his own memoir, entitled The Journey, later this year but was pipped to the post by his former right-hand man, who signed copies at a bookshop appearance in London yesterday afternoon.